An interactive and remote maintenance system has been well known. It is used for searching for the cause of an electrical problem in a machine and repairing it. It utilizes a communication line such as a telephone line (e.g., Japanese Patent Laid-open Publication No. 2002-41132).
The system disclosed in that publication uses a video camera that is placed near the machine. Thus it is not appropriate for a remote assistant system for a large plant such as a molding line that includes a molding machine or a casting line that includes a pouring machine in a foundry, because a fixed video camera cannot detect all locations of trouble in a large plant. Further, since the layouts of foundries differ depending on the goods that are cast, production lots, or foundry processes, the position of the video camera cannot be definitely determined. In addition, it is difficult for operators to remember the names of many parts of the machines. It is also difficult to understand the relationships between these parts. It is not easy to judge if the trouble is caused by the molding machine or by the molding line.
An assistant, who is at a remote location away from the foundry, has a similar problem in assisting the operator. Since the layouts of foundries differ depending on the plants, it is difficult to forecast the location of trouble in a molding machine or a molding line. Thus it is difficult for an assistant who is at the remote location to quickly instruct the operator on what he or she should do. Even if the location of the trouble is found, the conventional fixed video camera is generally located far from the location. Thus it is difficult to quickly realize the cause of the trouble and give instructions to repair the cause. Further, if information on a ladder logic program is merely used for making repairs, an unexpected circumstance may occur, because the machine or line may be reactivated without the safety being checked. For example, there may be an obstacle in the way of a part in the plant that is being moved. Or, there may be a person near the plant. Thus there has been a need for a system for remote assistance that is safer.
Further, the interactive and remote maintenance system disclosed in the publication is supposed to have only one PLC (Programmable Logic Controller; see FIG. 1, etc., of the publication). Thus, when a plurality of PLCs is installed in each molding machine or molding line, information by video images that are taken by a fixed video camera cannot be used. Therefore it is difficult for the assistant at the remote location to give instructions regarding the PLC and the location of the trouble to the operator, who is far from the assistant. Especially, in an urgent case, since the operator is not accustomed to such operations, the assistance is more important.